如何破坏包含三个列表的List元素，这样我就可以创建一个列表来添加到数据库中

Question

Web API的内容是这个JSON字符串，并且反序列化为：

List<AddAssignMealView> mealtraiDeserializeObjects = JsonConvert.DeserializeObject<List<AddAssignMealView>>(mealTrainee);

mealtraiDeserializeObjects包含五个索引，每周一天。在该特定索引内部是一个类似于以下内容的类：

public class AddAssignMealView
{
    public int TraineeID { get; set; }
    public string DayOfTheWeek { get; set; }
    public List<string> MealTypes { get; set; }
    public List<int> MealID { get; set; }
    public List<string> MealName { get; set; }
}

我想要做的是，能够创建一个MealTrainee（实体框架）列表：

 public partial class MealTrainee
{
    public int MealTraineeID { get; set; } //Ignore this one due to it being a post
    public int MealID { get; set; }
    public int TraineeID { get; set; }
    public string DayOfTheWeek { get; set; }
    public string MealType { get; set; }
    public string MealName { get; set; }

    public virtual Meal Meal { get; set; }
}

所以我可以使用addrange并将列表添加到数据库中。我理解如何使用zip并将两个列表类型组合在一起（如果它是单个元素）。这是不同的，因为它是五个元素的列表，并且这五个元素中的每一个都包含三个列表。如果有人能指出我正确的方向，那将会有所帮助。

Answer 1

你可以Zip 2次将3个列表中的值组合成一系列元组。您可以使用SelectMany来平整结果。例如：

var result = mealtraiDeserializeObjects.SelectMany(c =>
    c.MealID.Zip(c.MealName, (id,name) => new {id, name})
    .Zip(c.MealTypes, (prev, type) => new {prev.id, prev.name, type})
    .Select(r => new MealTrainee
    {
        TraineeID = c.TraineeID,
        DayOfTheWeek = c.DayOfTheWeek,
        MealID = r.id,
        MealName = r.name,
        MealType = r.type,
    }));

Answer 2

这是我找到的解决方案。我认为第一次迭代将是星期一，然后是用餐次数（例如：早餐用餐，午餐用餐），并将它们计入“每周一餐”。然后我每周吃一顿饭，为每个计数创造一个新的餐馆。然后在我从饭柜中取出饭后，我把它放在db.MealTrainees.AddRange并张贴了所有记录。

    [ResponseType(typeof(MealTrainee))]
    public IHttpActionResult PostMealTrainee([FromBody] string mealTrainee)
    {
        List<MealTrainee> meals = new List<MealTrainee>();

        using (DbContextTransaction dbContextTransaction = db.Database.BeginTransaction())
        {
            try
            {
                List<AddAssignMealView> mealtraiDeserializeObjects = JsonConvert.DeserializeObject<List<AddAssignMealView>>(mealTrainee);

                foreach (var mealtraiDeserializeObject in mealtraiDeserializeObjects)
                {
                    var mealWeek = mealtraiDeserializeObject.MealID.Select((m, i) => new
                    {
                        mealtraiDeserializeObject.TraineeID,
                        mealtraiDeserializeObject.DayOfTheWeek,
                        MealID = m,
                        MealTypes = mealtraiDeserializeObject.MealName[i],
                        MealName = mealtraiDeserializeObject.MealTypes[i]
                    }).ToList();

                 var meal = mealWeek.Select(x => new MealTrainee()
                    {
                        DayOfTheWeek = x.DayOfTheWeek,
                        MealID = x.MealID,
                        MealName = x.MealName,
                        MealType = x.MealTypes,
                        TraineeID = x.TraineeID
                    }).ToList();

                    db.MealTrainees.AddRange(meal);
                }

                if (!ModelState.IsValid)
                {
                    return BadRequest(ModelState);
                }

                db.SaveChanges();
                dbContextTransaction.Commit();
                return Ok(meals);
            }
            catch (Exception e)
            {
                dbContextTransaction.Rollback();
                Logger.Log(e);
                return BadRequest();
            }
        }
    }